1. Field of the Invention
The present invention relates to temperature control of a heat furnace in hot rolling line, wherein furnace temperature setting value to minimize fuel amount and mixed combustion ratio of plural fuels are set.
2. Description of the Prior Art
Temperature control of such heat furnace in the prior art is disclosed, for example, in Japanese examined patent publication No. 48011/1983, wherein both non-linear models, model to calculate material temperature from furnace temperature and model to calculate fuel flow rate from the furnace temperature and the material temperature, are used, the furnace temperature is varied in steps and linearization is performed using perturbation simulation method (method of performing simulation at the reference state and the perturbation state and determining the linearization coefficient) in order to minimize the non-linear fuel amount, temperature rise curve of the material is determined using results of the linearization, and the temperature rise curve and the existing temperature of the material are compared so as to determine the furnace temperature.
In above-mentioned heating control method of a heat furnace in the prior art, since the calculation zones of furnace temperature are usually larger in number than the zones to control the fuel flow rate as shown in FIG. 1, the optimum furnace temperature and the temperature rise curve after optimization by the perturbation method based on the furnace temperature are not always the realizable pattern.
When the linearization coefficient and the temperature rise pattern are determined, since the amount of heat loss to a furnace wall, temperature distribution in the furnace wall and the like are ignored and the simulation is performed by varying the furnace temperature stepwise without taking into consideration response delay of the furnace, the temperature rise curve being different from the actual temperature rise tendency of the material and state of the furnace may be determined.
Also in the method of the prior art, as shown in FIG. 2, a furnace temperature detector 104 to obtain feedback signal is installed at one position per each control region 101a. Consequently, it can control the furnace temperature of one position.
In a heat furnace in general, since the material temperature becomes higher in a position closer to the extraction end, a burner is designed so that the temperature at the burner side becomes high as shown in FIG. 2. When the low load material exists at the front side and the high load material exists at the rear side within the control region as shown in FIG. 2, the furnace temperature is controlled corresponding to the temperature within the furnace desired for the high load material. Consequently, the furnace temperature is set inevitably to higher value, resulting in large loss from the viewpoint of fuel consumption.